"It is also recognized that paternal age is increased among affected children."

1: Nat Rev Genet. 2008 May;9(5):341-55. Links
Advances in autism genetics: on the threshold of a new neurobiology.Abrahams BS, Geschwind DH.
Neurology Department, and Semel Institute for Neuroscience and Behaviour, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095-1769 USA. brett.abrahams@gmail.com

Autism is a heterogeneous syndrome defined by impairments in three core domains: social interaction, language and range of interests. Recent work has led to the identification of several autism susceptibility genes and an increased appreciation of the contribution of de novo and inherited copy number variation. Promising strategies are also being applied to identify common genetic risk variants. Systems biology approaches, including array-based expression profiling, are poised to provide additional insights into this group of disorders, in which heterogeneity, both genetic and phenotypic, is emerging as a dominant theme.